High-voltage, gas filled tubes have been widely used for signage for decades. With such tubes, it is necessary to connect a high voltage conductor with a tube electrode inside an electrode receptacle. Such an electrode receptacle is subject to degraded performance due to moisture condensing in the receptacle finding its way to a ground outside the receptacle, thereby causing damage to the gas filled tube and its associated electrical circuits and components. A known connection of a gas filled tube, for example, a neon tube to a high voltage conductor is illustrated in FIG. 4. The neon tube 20 is mounted within a channel housing 22, for example, an aluminum casing, that supports a face or lens 24 through which the neon tube 20 is viewed. The neon tube 20 has an electrode 26 with an electrode contact 27 to which a high-voltage potential is supplied by means of a conductor or wire, for example, a high voltage gaseous tube and oil ignition ("GTO") cable, 28. The voltage is in the kilovolt range; and therefore, it is important that the connection between the cable 28 and the electrode 26 be easily made and further, that the connection be reliable over a period of use. In many applications, the connection between the electrode 26 and the high-voltage cable 28 is accomplished utilizing a known electrode receptacle 30 which is often implemented with a connector P-K connector. The electrode receptacle 30 is comprised of an outer protective housing, for example, a metal tube, 32 that is connected to an inner insulator tube, for example, a glass insert, 34 by means of respective threads 36a, 36b.
A mounting plate 38 supporting the channel housing 22 is mounted to a structure, for example, a surface, 40 often an exterior surface, of a wall 42. Thereafter, the insulator tube 34 is passed through a bore 44 within the mounting plate 38 and a hole 46 in the wall 42. The metal housing 32 is then inserted through the hole 46 of the wall 42 from an opposite side 48 and over the insulator tube 34. The metal housing 32 is then rotated with respect to the insulator tube 34 to engage the threads 36a, 36b on the housing 32 and tube 34, respectively. As the metal housing 32 is tightened, an end surface 50 of the housing 32 engages a gasket 52 located between the end surface 50 and a rear side 53 of the mounting plate 38. In addition, a mounting flange 54 on the open end of the insulator tube 34 presses against a gasket 56 and the front surface 58 of the mounting plate 38. Thus, the metal housing 32 and insulator tube 34 cooperate to securely mount the electrode receptacle 30 within the wall 42 to the mounting plate 38. Thereafter, the cable 28 is passed through openings 33, 90, in the respective closed ends 82, 35 of the insulator tube 34 and the metal housing 32. A spring contact 66 is then crimped onto the end of the cable 28 in a known manner and located on a shoulder 67 within the insulator tube 34. The cable 28 is carried within a conduit 60 mechanically connected via a conduit connector 62 to internal threads of a nut 64 on the bottom 35 of the metal housing 32. With the cable 28 secured within the electrode receptacle 30, the electrode 26 is inserted into the glass insulator tube 34, and its electrode contact 27 is pushed into contact with the spring contact 66, thereby providing a connection to the high-voltage cable 28. One or more tube supports 68 attached to the neon tube 20 are then fastened to the mounting plate 38 by known means.
The electrode receptacle 30 normally provides a reliable, high-voltage connection between the cable 28 and the electrode 26. However, over time, two failure conditions may arise. First, the thermal cycling of the neon tube 20 and the electrode receptacle 30 often results in the formation of condensation on the inside surface 70 of the insulator tube 34 or the metal housing 32. If moisture weeps along the outer surface of the cable 28, there is the potential for small current paths to be created between the spring contact 66 and ground, for example, the metal housing 32 and/or the conduit 60 and its connector 62. Depending on the extent of moisture on the cable 28, those current paths may be small or large, however, in any case, the current paths will cause a short circuit and failure in the lighting circuit.
A second problem with a typical electrode receptacle is that as the cable 28 passes through the bottom of the metal housing 32, for example, through the nut 64 and into the conduit 60, it is possible for the outer insulation of the cable 28 to be nicked or otherwise damaged by those metal components. For example, the nut 64 on the end of the metal housing 32 has internal threads that accept a threaded portion of a conduit connector 62. Any nick or other damage to the insulation of the cable 28 reduces the integrity and effectiveness of the insulating properties and, over time, often results in a failure and short circuit condition. In addition, any nicking or degradation of the insulation of the cable 28 is magnified by the presence of condensation or moisture on the outer surface of the cable 28 that also provides a low resistance current path to the metal housing 32 or conduit 60 and connector 62.
Therefore, there is a need for an improved connector housing a high-voltage connection between a high-voltage conductor and a gas filled tube, such as a neon tube.